A significant amount of the published and well known casting technology relating to high temperature operating articles, for example turbine blades for gas turbine engines, has centered about improvement of certain properties through elimination of some or all of the grain boundaries in the final article's microstructure. In general, such structures have been generated by the well known precision casting techniques of solidifying a molten metal directionally (directional solidification) to cause the solidifying crystals or grains to be elongated. If only one grain is allowed to grow in the article during solidification, for example, through choking out others or using a seed crystal, an article of a single crystal and substantially no grain boundaries results. However, if multiple grains are allowed to solidify at an area of a casting mold and allowed to grow generally in a single direction in which heat is withdrawn from molten metal in a casting mold, multiple elongated or columnar grains exist in the solidified casting. Such a structure sometimes herein is called "DS multigrain" in connection with a cast article. The direction of elongation is called the longitudinal direction; the direction generally normal to the longitudinal direction is called the transverse direction.
Because the grain boundaries in such an article are substantially all longitudinal grain boundaries, it is important in an article casting that longitudinal mechanical properties, such as stress rupture life and ductility, be very good, along with good transverse mechanical properties and good alloy surface stability. With this property balance in the article, the article alloy must be capable of being cast and directionally solidified in complex shapes and generally with complex internal cavities and relatively thin walls without cracking. So called "thin-wall" hollow castings have presented difficult quality problems to article casters using the well known "lost wax" type of precision casting methods with alloys designed for improved properties: though the alloy properties are good and within desired limits, thin wall castings, for example with a wall less than about 0.035 inch thick, generally cracked during multicolumnar grain directional solidification.